On polyacrylamide gel electrophoresis, transcortin migrates in two bands, both of which bind cortisol. Upon isoelectric focusing, each of these resolves into 6 - 7 bands. Asialotranscortin has about one-half the number of bands. Our objective is the accumulation of sufficient material so that we can determine whether all these members of the transcortin family bind cortisol, their carbohydrate and amino acid composition and fingerprint patterns. These results would answer conclusively the question of whether transcortin is actually a family of proteins. If so, it would provide an explanation for the series of discordant results reported.